Gardenia-derived edible dyes: gardenia blue, gardenia red, and gardenia yellow have hitherto been used.
“Gardenia blue” is generally obtained by subjecting an iridoid glucoside (whose major component is geniposide), obtained by extraction from gardenia fruits (Gardenia augusta Merrill var. grandiflora Hort., Gardenia jasminoides Ellis) of the family Rubiaceae, to a β-glucosidase treatment in the presence of a proteolytic product or the like. Geniposide is converted into genipin (aglycone) by a β-glucosidase treatment, and genipin is reacted with a proteolytic product or the like, thereby generating a gardenia blue colorant component (coloring principle).
Therefore, generally, “gardenia blue” is not a single compound, but a mixture. “Gardenia blue” generally contains raw material-derived unreacted geniposide or genipin or both. To the best of the Applicant's knowledge, a method for highly removing geniposide and genipin from gardenia blue has not been established; therefore, geniposide or genipin or both are contained even in purified gardenia blue.
“Gardenia red” is generally obtained by subjecting an ester hydrolysate (whose major component is geniposidic acid, which is a hydrolysate of geniposide) of an iridoid glucoside (whose major component is geniposide), obtained by extraction from gardenia fruits of the family Rubiaceae, to a β-glucosidase treatment in the presence of a proteolytic product.
Therefore, generally, “gardenia red” is not a single compound, but a mixture. “Gardenia red” generally contains raw material-derived unreacted geniposide, genipin generated from the unreacted geniposide, or both. To the best of the Applicant's knowledge, a method for highly removing geniposide and genipin from gardenia red has not been established; therefore, geniposide or genipin or both are contained even in purified gardenia red.
“Gardenia yellow” is generally obtained by aqueous extraction or hydrous ethanol extraction of gardenia fruits of the family Rubiaceae. The major colorant components of “gardenia yellow” are crocin and crocetin.
Therefore, “gardenia yellow” is also not a single compound, and generally contains raw material-derived geniposide.
Genipap (Genipa americana L.) juice (also known as huito juice) or its extract, which has been widely used for beverages and food, also contains genipin.
As in these examples, foods and food additives containing geniposide or genipin have hitherto been used without major problems.
However, Non-patent Document 1 discloses that oral administration of a large amount of geniposide to rat induced hepatotoxicity, and that the expression of the toxicity may be relevant to genipin generated by intestinal bacteria β-glucosidase in rat.
Further, intake of food or beverage containing genipin such as genipap juice poses a problem such that the genipin bonds to a protein in the skin around the mouth, thereby turning the skin around the mouth blue.
Regarding geniposide removal, Patent Document 1 discloses a technique of selectively adsorbing crocin, which is a colorant component of gardenia yellow, to a specific synthetic adsorption resin; this thereby removes an iridoid glucoside containing, as a major component, geniposide, which causes discoloration of gardenia yellow into green.
Patent Document 1 further discloses that it is not possible to separate geniposide from the colorant component of gardenia yellow by an activated carbon treatment, since activated carbon non-selectively adsorbs both the colorant component of gardenia yellow and geniposide.